The electronic structure of the (LiYb)$^+$ molecular ion is investigated with two variants of the coupled cluster method restricted to single, double, and noniterative or linear triple excitations. Potential energy curves for the ground and excited states, permanent and transition electric dipole movements, and long-range interaction coefficients $C_4$ and $C_6$ are reported. The data is subsequently employed in scattering calculations and photoassociation studies. Feshbach resonances are shown to be measurable despite the ion's micromotion in the Paul trap. Molecular ions can be formed in their singlet electronic ground state by one-photon photoassociation and in triplet states by two-photon photoassociation; and control of cold atom-ion chemistry based on Feshbach resonances should be feasible. Conditions for sympathetic cooling of an Yb$^+$ ion by an ultracold gas of Li atoms are found to be favorable in the temperature range of 10$\,$mK to 10$\,$nK; and further improvements using Feshbach resonances should be possible. Overall, these results suggest excellent prospects for building a quantum simulator with ultracold Yb$^+$ ions and Li atoms.
Ultracold Rb-OH collisions and prospects for sympathetic cooling
本文计算了Rb原子与OH自由基冷碰撞的从头算截面。我们预测，在10-100 mK的温度范围内，碰撞速率常数为10^{-11} cm ^3/s，在此温度下，分子已经在实验中产生。然而，我们也发现，在这些碰撞的分子有很强的倾向，改变其内部状态，这可能会使共振冷却的Rb缓冲气体中的OH的问题，在静磁或静电陷阱。
Cold collisions of heavy $^2Σ$ molecules with alkali-metal atoms in a magnetic field: Ab initio analysis and prospects for sympathetic cooling of SrOH$(^2Σ)$ by Li($^2$S)
We report on the experimental observation of Feshbach resonances in large mass-imbalance mixtures of Erbium (Er) and Lithium (Li). All combinations between ${}^{168}$Er, ${}^{166}$Er and ${}^7$Li, ${}^6$Li are cooled to temperatures of a few microkelvin, partially by means of sympathetic cooling together with Ytterbium (Yb) as a third mixture component. The Er-Li inelastic interspecies collisional properties are studied for magnetic fields up to 680 G. In all cases resonant interspecies loss features, indicative of Feshbach resonances, have been observed. While most resonances have sub-Gauss w…
Sympathetic cooling of fluorine atoms with ultracold atomic hydrogen
我们考虑了利用超冷氢原子将氟原子共振冷却到微开尔文温度的前景。我们进行量子力学计算的冷F和H原子之间的碰撞磁陷阱状态，并表明，弹性与非弹性截面的比例仍然很高，在很宽的温度范围和磁场。对于最初处于自旋拉伸状态的F原子（$^2$ P $_{3/2}$，$f=m_f=+2$），交感冷却似乎可能从大约1 K甚至更高的起始温度成功。这是因为非弹性碰撞被分别为600 mK和3.2 K高的p波和d波势垒抑制。结合H + NH和H + OH碰撞的最新结果[M. L. González-Mart\'ınez和J. M. Hutson，arXiv：1305.6282（2013）]，这确立了超冷H原子作为用于不能被激光冷却的原子和分子的非常有前途和通用的冷却剂。
Controlling physical systems and their dynamics on the level of individual quanta propels both fundamental science and quantum technologies. Trapped atomic and molecular systems, neutral and charged, are at the forefront of quantum science. Their extraordinary level of control is evidenced by numerous applications in quantum information processing and quantum metrology. Studying the long-range interactions between these systems when combined in a hybrid atom-ion trap has lead to landmark results. Reaching the ultracold regime, however, where quantum mechanics dominates the interaction, e.g., g…
Charge transfer in ultracold gases via Feshbach resonances
我们研究了在同元素原子和离子的异源同位素组合的超冷碰撞中控制电荷交换的前景。这种处理方法很容易应用于碱金属或链烷烃-土金属，如过程$^9$ Be $^{+}$ + $^{10}$ Be $\leftrightarrow$ $^{9}$ Be + $^{10}$ Be $^{+}$所示，它具有良好的电子、核和超精细结构。费什巴赫共振得到的量子散射计算在一个标准的耦合通道形式主义与非BO条款起源于核动力学运营商。在322 G处预测的窄共振附近，我们发现电荷交换速率系数从几乎为零上升到大于$10^{-12}$ cm $^3$ /s的值。我们的研究结果表明，可控的电荷交换反应之间的不同同位素的合适的原子-离子对与潜在的应用量子系统工程研究电荷扩散被困冷原子-离子混合物和模拟多体物理。
Magnetically tunable Feshbach resonances exist in ultracold collisions between atoms in $^2$S and $^3$P$_0$ states, such as an alkali-metal atom colliding with Yb or Sr in a clock state. We investigate the mechanisms of these resonances and identify the terms in the collision Hamiltonian responsible for them. They involve indirect coupling between the open and closed channels, via intermediate channels involving atoms in $^3$P$_1$ states. The resonance widths are generally proportional to the square of the magnetic field and are strongly enhanced when the magnitude of the background scattering…
We have investigated Feshbach resonances in collisions of high-spin atoms such as Er and Dy with closed-shell atoms such as Sr and Yb, using coupled-channel scattering and bound-state calculations. We consider both low-anisotropy and high-anisotropy limits. In both regimes we find many resonances with a wide variety of widths. The wider resonances are suitable for tuning interatomic interactions, while some of the narrower resonances are highly suitable for magnetoassociation to form high-spin molecules. These molecules might be transferred to short-range states, where they would have large ma…
Optical tuning of the scattering length of cold alkaline earth atoms
利用光学费什巴赫共振可以调节超冷1 S 0基态碱土原子碰撞的散射长度。这是实现与激光远失谐的激发分子水平附近的频率的原子相互结合1 S 0 - 3 P1过渡。简单的共振散射理论，说明了40钙的例子，允许估计的影响的大小。与碱金属物种不同，由于分子光缔合跃迁的线宽非常窄，散射长度的大变化是可能的，而原子损失仍然很小。这为没有磁调谐费什巴赫共振能级的系统控制原子相互作用提出了前景。
Atomic clocks based on an Al$^+$ ion sympathetically cooled by a laser-cooled alkaline-earth ion have achieved unprecedented accuracy. Here, we investigate theoretically interactions and charge transfer dynamics of an Al$^+$ ion immersed in an ultracold gas of Rb and Sr atoms. We calculate potential energy curves and transition electric dipole moments for the (Al+Rb)$^+$ and (Al+Sr)$^+$ ion-atom systems using coupled cluster and multireference configuration interaction methods with scalar relativistic effects included within the small-core energy-consistent pseudopotentials in Rb and Sr atoms.…
We reflect on the prospect of exploiting the recoil associated with absorption and emission of photons to perform spectroscopy of a single molecular ion. For this recoil to be detectable, the molecular ion is sympathetically cooled by a laser-cooled atomic ion to near their common quantum mechanical ground state within a trapping potential. More specifically, we present a general framework for simulating the expected photon recoil spectra in regimes where either the natural transition linewidth $Γ_t$ of the molecular ion or the spectral width $Γ_L$ of the exciting light source exceeds the moti…
Collisions with cold particles can dissipate the energy of a hot particle and therefore be exploited as a cooling mechanism. Kinetics teaches us that for a particle to be cooled down by several orders of magnitude, it will typically take many elastic collisions as each one only carries away a certain fraction of the collision energy. Recently, for a system consisting of hot ions and cold atoms, a much faster cooling process has been suggested where cooling over several orders of magnitude can occur in a single step. Namely, in a homo-nuclear atom-ion collision, an electron can resonantly hop f…
